Myotonic dystrophy is the most common adult muscular dystrophy in the world. Despite an emergent need, no disease-specific, quality-of-life instrument has ever been developed for this population. If funded, this K-23 application will address this need while providing the ideal environment for Dr. Heatwole to complete his training enroute to becoming an independent researcher of novel evaluation techniques and experimental therapeutics for muscle diseases. Specifically, it is our goal to: 1) Identify the symptomatic and functional areas most relevant to myotonic dystrophy type-1 patients; 2) Develop a question set capable of measuring these domains; 3) Test the responsiveness of this question set in a longitudinal study; 4) Utilize item response theory and advanced statistical methods to develop a responsive and reproducible instrument from this question set; 5) Incorporate this instrument into one current and two planned clinical trials of myotonic dystrophy patients; and 6) Develop additional disease-specific instruments for facioscapulohumeral muscular dystrophy and the more recently described myotonic dystrophy type-2. We hypothesize that this project will positively shape public health by enabling researchers to measure treatment responses in myotonic dystrophy via a valid, efficient set of disease-specific questions. In addition, through these projects, we plan to lay the methodological and technical framework needed for the development of additional disease-specific instruments for muscular disorders. The mentored clinical investigator career development award in muscle disease research provides the ideal medium for Dr. Heatwole to become an independent neuromuscular researcher and authority on instruments of quality-of-life. Dr. Heatwole's career development will be facilitated by: 1) An expert multidisciplinary mentorship team; 2) Scientific didactic lectures and workshops leading to a Master of Science in Clinical Investigation; and 3) By direct access to the Clinical and Translational Science Institute's facilities designed specifically to conduct and promote clinical research. By the end of the K-23 funding period it is Dr. Heatwole's explicit plan to have a nationally recognized laboratory established in both myotonic dystrophy experimental therapeutics and muscle disease quality-of-life instrumentation.